Field
Embodiments described herein generally relate to doping of three dimensional (3D) structures formed on a substrate. More specifically, embodiments described herein relate to conformal doping in 3D silicon structures using conformal dopant deposition processes.
Description of the Related Art
Three dimensional (3D) transistors, such as fin field-effect transistors (FinFETs) are promising candidates to extend complimentary metal-oxide semiconductor (CMOS) scaling. Such FinFET transistors generally provide for improved electrostatic control (i.e. short channel effects) and lower sensitivity to random dopant fluctuations. However, implementation challenges and process complexity issues exist in the integration of FinFETs at advanced technology dimensions.
For example, one challenge of FinFET integration is dopant concentration in 3D silicon containing device structures. As a result of the lack of a body or back gate bias in fully depleted (i.e. no mobile carriers) FinFET device structures, complicated workfunction engineering is often necessary to achieve workable threshold voltages for undoped FinFETs. In addition to threshold voltage complications, dopant concentration and dopant distribution within the FinFET structures present additional challenges in 3D device structure manufacturing processes.
Current FinFET doping processes utilize angled ion implantation schemes or line of sigh deposition schemes. In angled ion implantation schemes, dopant concentration and distribution specificity is difficult to control and such systems are expensive to implement in processing sequences. Additionally, throughput may be negatively affected with additional apparatus used to perform doping operations. Line of sight schemes may be used to deposit dopant films on FinFETs, but the 3D structure of FinFETs prevent suitable film deposition characteristics (i.e. deposition on sidewalls of 3D structures) which adversely affects dopant distribution and concentration within the FinFET structures.
Accordingly, there is a need in the art for improved FinFET doping methods.